B121

Code B121 - Twilight Enable Switch Circuit:

Wiring Diagram for Codes B119, B120, B121, B122 & B123:

CODE B121 - TWILIGHT ENABLE SWITCH CIRCUIT

Circuit Description:

The twilight enable switch uses the same physical control as the delay pot. Inside the left switch assembly the enable switch contacts close as soon as the time delay slider is moved off of its extreme min. (off) position. The BCM supplies a voltage on CKT 304 to the switch. When the slider is moved from the off position the switch contacts close and the signal voltage is pulled low through ground CKT 804.

Code B121 will set if the ignition is on, the twilight delay pot has not failed (Code B120) and the signal voltage is high when the delay slider is moved from the off position (open CKT).


Test Description:

1. BCM input value B182 displays the voltage state of the circuit at the BCM. These conditions can be observed in BCM input display BI82 as readings of HI or LO when delay slider is moved.

2. Checks to see if the HI reading is due to the circuit or the switch assembly. If the display changes from "HI" to "LO" when the switch terminals are jumpered, the BCM and wiring are OK.

3. Check to see if the HI reading is due to the circuit or the BCM. If the display changes from "HI" to "LO" when the BCM terminal cavity is jumpered to ground, the BCM is OK.


Note on Intermittents:

If an intermittent code B121 is being set, manipulate CKT 304. When BCM B182 input change-of-state indicator displays an "X" check the circuit for an intermittent open.

Cycle twilight control between off and max delay. If BCM data, BD43, does not read 6 to 94%, then replace left switch assembly.